Our overall hypothesis is that ordered therapy with oncoprotein disabling mAb followed by IFN-? leads to phenotypic changes in tumor cells never achieved with mAb itself. MAb induced phenotypic changes sensitize cells or are permissive for unexpected actions of IFN-? directly on the tumor. The overall goal of this proposal is to gain a deeper understanding of events of erbB mediated tumorigenesis and to develop more potent therapeutics to treat and prevent the emergence of resistant tumor formation and spread. We will employ MMTV NeuT-tdTomato transgenic mice created to express MMTV-neu proteins in Tomato tagged mammary cells and which develop breast tumors stochastically much like human breast cancer. These unique transgenics will be subjected to the effects of targeted therapy against the p185 oncoprotein followed by or concurrent with IFN-? therapy. Tumor emergence and spread will be followed and cell lines developed from progressive tumors for further biochemical studies. Other studies will employ paired administration of anti-p185 mAb and IFN-?, as well as use of a new species of anti-erbB2-scFv with a modified effector domain to which we have genetically attached the IFN-? molecule. The MMTV NeuT-tdTomato transgenic mice will be hosts to follow the effects of mAb alone, or in combination with IFN-?, on tumor progression and metastatic spread. Resistant tumors that arise despite treatment with mAb to p185neu will be studied for phenotypic and allelic changes that occur in the tumor itself, through the use of propogated cell lines, in particular genes we have considered to be relevant to the malignant phenotype. Our studies on a newly engineered mAb humanized mAb-IFN-? recombinant protein fused with a humanized ZZ domain, (which we term the ZED domain) will be extended to Herceptin resistant breast cancers. This highly engineered mAb species simultaneously disables p185erbB2/neu kinases; amplifies immunoglobulin effects through the ZED domain; and, finally, delivers IFN-? directly to human tumor cells. We will evaluate if effector domain modified targeting anti-erbB2 mAb also affects cells transformed by both the erbB2/neu oncogene and other somatic mutations such as KiRas. This construct may be a prototype of a therapeutic for human disease. Finally, we will also evaluate if cytotoxic/genotoxic signals (such as the taxane, docetaxol) used with this new species of antibody further eliminates Herceptin resistant tumor cells.